A pair of 18-year-old girls spent several hours roaming an all-male school by dressing as boys for the day.

Tess Norquay and Julia Holden donned Wellington College uniforms earlier this year to see if they could go unnoticed. They then wrote about their covert operations in the latest Wellington High School magazine Flannel.

The assignment, approved by their journalism teacher Laurie Steel, passed off without their being noticed. The only hitch came when Julia was manhandled during a lunchtime football game.

She said she was picked up and removed from the field because she was a junior, not because she was a girl.

This, she said, proved they had pulled off the "slightly effeminate sullen third former look".

"We looked manlier than some of the year 9 pupils, to be honest."

They didn't go to any classes but milled around the libraries, hallways and playing fields for a few hours in July without any trouble.

Some of the year 9 boys were a bit suspicious, probably because of the girls' lack of offensive body odour mixed with Lynx deodorant, she said.

But their slight frames, blemish-free skin and higher-pitched voices didn't give them away.

"We both have quite low voices to begin with so it was OK - we just tried to go a bit lower," Tess said.

The pair also repeated their undercover roles at Wellington Girls' College.

"We tried to go about everyday activities they would do, so at Girls' we entered a poetry competition and at Coll we tried to play football and it went really badly."

Mr Steel said he had approved the assignment as they were smart and trustworthy pupils. "These are two of my best and brightest kids . . . with a very strong ethical substance to them."

It was done in good spirit and was a way to "perhaps poke a bit of fun at our rival schools without yelling abuse on the sideline".

Wellington Girls' College principal Julia Davidson said it wasn't the crime of the century but she didn't want "hundreds of kids" attempting the exercise.

She wasn't surprised they had blended in with her 1350 pupils. "You could do it in just about every school in the country.

"We don't put microchips on the kids and check them at every door of the school, so I don't know quite how we would address it."